Remember the classic anecdote about how they were filming after the movie had already won best picture? That was done solely for the EE.

Besides, remember they're doing pick-ups and a few months of extra filming next year, it's not exactly hard for them to shoot some more sound stage stuff. (Location might be a different story, but considering that even Rivendel is in the studio now, I imagine they have a lot of freedom).

Pretty much at this point, if Peter wants it, he'll get it. And if not, they'll just sneak it into the fine print of the schedules ; )